In general, a magnetic field sensor based on a MEMS (micro electro mechanical systems) capacitive sensing technology includes a driving electrode movable in reaction to a magnetic field and a fixing electrode to sense capacitance variation corresponding to the movement of the driving electrode.
According to the principle on the magnetic field sensor, when reference current is applied to the driving electrode in a predetermined direction, the driving is moved from the fixing electrode in a positive or negative direction due to the Lorentz force based on the direction and the intensity of an external magnetic field.
In this case, the variation in the distance between two electrodes or the overlap area between the two electrodes is made to vary the capacitance. The variation of the capacitance or the signal varied corresponding to the variation of the capacitance is detected to sense the magnetic field.
However, since the Lorentz force used to sense the magnetic field is relatively significantly small as compared to gravity, the design for a sensor assembly including a spring is limited, so that it is difficult to obtain sufficient mechanical displacement.
In addition, as the distance between a conductor through which current to be measured flows and the sensor is increased, the sensitivity of the magnetic field is decreased, so that the signal may not be exactly detected.
Meanwhile, recently, the conductor and the magnetic field sensor are formed in one package. As the conductor and the magnetic field sensor are arranged together in one receiving space, the intensity of the magnetic field is increased.
In the case of the magnetic field sensor, since the displacement difference of the driving electrode is made according to the direction of the magnetic field coming into the sensor assembly, the arrangement of the sensor assembly and the conductor must be appropriately performed.
FIG. 1 is a view showing the arrangement of a conductor through which current to be measured flows, and a sensor assembly in a sensor package according to the related art.
Referring to FIG. 1, the sensor package according to the related art includes a magnetic field sensor 10 including a sensor assembly 20, and a conductive line 30 provided on the magnetic field sensor 10 so that the current to be measured flows.
The conductive line 30 is vertically parallel to the sensor assembly 20 at a predetermined distance from the sensor assembly 20.
However, according to the sensor package described above, since the conductive line 30 is vertically parallel to the sensor assembly 20, the magnetic field comes into the sensor assembly 20 in a horizontal direction or an inclination direction.
Accordingly, since the magnetic field has the horizontal direction or the inclination direction, Lorentz force is vertically applied to the sensor assembly 20, so that the displacement of the sensor assembly may be reduced or abnormally driven.
If the displacement of the sensor assembly is reduced or abnormally driven as described above, the output single of the magnetic field sensor is reduced even under the current intensity, and the output value of the magnetic field sensor may be unstable.